Skirted die



Dec. 1, 1964 R. A. suTPHlN SKIRTED DIE Filed Jan. 6. 1961 E b .9... W. A

` BY @cf/ARD A G 5' ATTORNEYS United States Patent O m 3,159,699 SKIREEDDIE Richard A. Sutphin, Cincinnati, hio, assigner to The Procter itGamble Company, Cincinnati, hio, a corporation of hio Fied 1an. 6, 1961,Ser. No, 31,@3'7 S Claims. (Cl. 26d-32th This invention relates to diesadapted to form plastic materials into articles having a pin-die shapeand more particularly to dies adapted to stamp pin-die shaped bar soapsor detergents. y

Articles, such as bar soaps, have been formed into pindie shapes formany years. As used in the trade, an article having a pin-die shape Iisone which is adapted to be stamped by means of a die pair havingperipheral surfaces or lands adapted to meet iny substantialface-to-f-ace contact, in contrast to die stamping by means of a boxdie, or a pin-box die, wherein the peripheral edges of the opposedsurfaces which apply molding pressure to form the article are notbrought into contact. In the most familiar embodiments of the latterforms of dies, one die half is telescoped within a passageway in a boxportion, which passageway surrounds the other die half and provides themold surfaces interconnecting the peripheral edges of the die halves.Thuseither the box die, or the pin-box die,

stamps an article having ends and side panels with the surfaces thereofformed with a continuous flat band therearound as a result of beingmolded to the shape of the box passageway between the peripheral edgesof the die halves, whereas an article having a pin-die shape has no suchband.

As normally performed, the process of stamping pin-die shaped rbars isone wherein surplus material is extruded in all directions from theperiphery of the bar, necessitating a trimming operation which is eitherperformed manually or with a special automatic trimming mechanism builtinto or acting in conjunction with the die halves. If done manually, thetrimming process is expensive and frequently leaves a rough ridge aboutthe bar along the line at which the surplus material is separated.Automatic trimming, on the other hand, tends to produce a neater lookingtrim line but results in the deposit of the scrap surplus materialsurrounding the machinery and the die halves, compelling a continuousand diflicult cleanup and scrap collection operation.

Many formulations of soapy and/ or detergent (hereinafter referred tojointly as soap), although desirable from a product performancestandpoint, do not possess the degree of plasticity or reweldabilityconducive to good stamping operation. As now practiced, the stamping ofsuch formulations -into pin-die shaped bars frequently results in aproduct having a number of hairline cracks, substantially following thedirection of crystal orientation, in the side or on the face panels ofthe bar. This type of defect is particularly prevalent where a ploddermakes identical soap blanks for various shapes of bar soaps or where itis impractical to extrude blanks having a cross section approximatingthat of the finished bar.

These hairline cracks, which usually occur in two planes approximatelyperpendicular to each other and roughly at about an angle of 45 to thestamping direction as the soap blank is deformed in stamping, should notbe confused with the type of cracks known in the industry as dry cracksor with another form called wet cracks, both of which are controlled orcaused by the process or equipment used prior to the stamp or by thephysical characteristics of the soap itself. Hairline cracks of thenature intended to be corrected by this invention are serious qualitydefects since they not only detract from the appearance of the bar as itcomes from the die, but also are 3,159,599 Patented Dec. 1, 1964 ICCvisible for a period of time as the bar is used by the consumer.

It is an object of the present invention to obviate the abovediiliculties.

Another object of the pesent invention is to provide for pin-die shapedsoap products, a die which obviates the necessity of hand trimming ofsurplus material, which facilitates the collection of such surplusmaterial, and which eliminates objectional hairline cracks in the sideor on the face panels of the product.

Brieiiy stated, in accord-ance with one aspect of this invention, thereis provided a die for stamping plastic material into an article,comprising mating die halves each having a cavity 'bounded by a narrowland, and a skirt member having portions thereof cotniguous to and pariallel with the longitudinal lands of the die halves so as to prevent thelateral extrusion of the surplus plastic material.

While the specifica-tion concludes with claims particularly pointing outand distinctly claiming the subject matter which is regarded as thepresent invention, it is believed that the invention wi-ll be betterunderstood from the following description of a preferred embodimenttaken in connection with the accompanying drawings in which:

FIGURE l is a perspective view showing a skirted die of this inventionwith a soap blank between the die halves;

FIGURE 2 is a section of the skirted die of FIGURE l taken along lineZ-Z thereof;

FIGURE 3 is a section similar to that of FiGURE 2, taken at the time theskirted die has made a full impression on the soapblank; v

FIGURE 4 is a perspective View from above showin the skirted die half ofFIGURE l; and

FIGURE 5 is a section similar to that of FIGURE 3, showing an embodimentutilizing means to prevent direct contact between the die halves.

Referring to FIGURE l, an exemplary soap blank 11 is shown intermediatea pair of mating die halves, upper die half 12 and lower die half 13, ina position to be stamped between the die halves 12 and 13 so as to bemolded to the shape of the die cavities 14. The soap blank 11 which ispreferably milled soap, is taken as a freshly cut piece of a continuousextrusion of soap produced by a soap plodden At this time the soap blank11 is in a warm and plastic condition and is best suited for the.stamping operation since the blank 11 must be considerably deformed inorder to be made to conform to the die cavities 14. As in other stampingoperations a stamp die liquor, such as a brine solution, is used as alubricating and release agent, preferably by application of the liquorto the soap blank 11 before the placement thereof in position for thestamping operation. The specific liquor used `and the .method of itsapplication, of course, are matters of choice and many variationsthereof are well known in the art.

The continuously extruded long bar from the soap plodder has a grainstructure of crystalline arrangement which has been oriented in thedirection of the extrusion, Since the soap blank 11 is cut from the longbar, it, too, has a grain in the extrusion direction-in this caselengthwise of the blank 11. Although it is possible that blanks 11 couldbe prepared with the grain running oppositely, i.e., transverse the longdimension, such is not usually the case. For this reason, as used hereinthe terms lengthf or longitudinaL or other words distinguishing `onedimension or side from the other planar dimensions in terms of greaterphysical size, should be interpreted as meaning the dimension of the dieor blank which parallels the ,grain of the soap. Similarly, the termswidt across, lateraL and other like descriptive words are intended torefer to the dimension of the die or blank which is transverse thedirection of the grain The soap blank 11 must, as in all similarstamping operations, be made to an optimum diameter for economy and bestresults for the size and shape of the bar being produced. This is amatter of experience once the dies have been prepared, and need not bediscussed in detail herein. Along this same line, it is usual to cut thesoap blank 11 longer than the die length by a finite amount to avoidwhat is termed a water mark in the industry. A water mark is the line ofseparation of two different or distinct shades of the color of the soapin a single bar and is usually found at each end of bars stamped fromblanks shorter than the die length.

Each of the die halves, both upper die half 12 and lower die half 13,have cavities 14 formed therein which follow the contours of theexterior surface of the portion of the bar intended to be moldedthereby. The outer surfaces of the die halves of the'exemplary apparatusparallel the direction of die motion, thus being vertical. Thesevertical surfaces are identical in shape and each is perpendicular tothe plane of the die face within which the cavity 14 is formed and has across section with a periphery which parallels the peripheral edge ofits respective cavity.

Although such is not shown in the figures, various designs or printedmatter could be engraved upon, or placed in bas-relief on, the surfaceof the cavities 14 so as to decorate and/ or, identify the source of thebar produced by the die. Such, of course, is a common practice andpresently Well known to those skilled in the art. Similarly otherfeatures well known in the industry could be incorporated in the diehalves to promote production and ease of operation, for example, the useof ejectors to aid in the removal of the finished bar from the dies andthe provision of passageways for the circulation of coolant through thedie halves. While these features might operate to facilitate thestamping operation, they are not essential to the present invention andtherefore not described in detail herein in order to set forth the bestmode of carrying out the invention.

The cavities 14 are each surrounded by a continuous land 15 ofrelatively narrow width dened by the peripheral edge of the cavities 14and the outer vertical surface of the die halves. Preferably, for thenormal range of bar sizes the width of land 15 should be less than 1/16"in order to eliminate the necessity of trimming. When thus dimensionedand upon the application of sufcient pressure during the stampingoperation, any surplus soap extruded from the dies will be pinched offbetween the opposed mating lands 15, and the side panels and the ends ofthe bar will be clear of all such surplus. When stamping bars of milledsoap which are of a size normally referred to as regular (i.e., havingdimensions roughly in the range of 2" to 2% in width and 3 to 31/2 inlength) a force of from 8,000 to 10,000 pounds on the die plunger and ahold time of approximately 0.5 second is normally sucient to obviate thenecessity of a scrap trimming operation. In this range of pressures, ithas been `found that lands 15 which are narrower than IAQ wear at larapid rate and are highly susceptible to damage caused by the pressuresinvolved in stamping and by other extraneous causes unless externalstops, such as are illustrated in FIG. 5, are provided to prevent actualcontact of the `opposed lands. Lands 15, however, which are wider thanlAG" do not satisfactorily pinch off the extruded scrap in the absenceof considerably higher pressures than used in conjunction with a narrowland and/ or a lengthy hold time for the die halves in the fullimpression positions. For these reasons, it is highly desirable forproduction dies to be made with lands 15 having a width of less than1/1(;" to increase speed and decrease machine load, and if no externalstops are used, to keep the width in the range of 16,2 to 1AG for longerdie life.

With respect to what has been termed a pinching off of the extrudedscrap, it should be noted that in stamping regular size bars, if the diehalves 12 and 13 (having lands 15 in the preferred range) are used witha force on the die plunger of about 8,000 pounds, the extrusion betweenthe lands 15 will persist as a thin membranous sheet for approximately 4seconds before becoming separated from the bar. It has been found,however, that despite this fact, a separation of the extrusion from thebar may be effected after the above-mentioned 0.5 second hold time. Themechanism of this separation is believed to be the fracture of themembranous sheet along the periphery of the bar, caused by tensilestresses developed in the sheet by bar expansive action following thecessation of bar compressions. The expansive action (due to internalpressures in the soap causing the bar to expand slightly in thicknesswhen the die pressure is reduced) results in a slight movement of thebar relative to the membrane and the tensile failure of the latter. Inany event, it will be seen that to pinch off the scrap extrusion, theopposed lands 15 do not have to be in direct contact and that theaforementioned possibility of external stops is practical inaccomplishing the desired result. As used herein, terms such as pinchoff should be interpreted as meaning separation as accomplished byeither squeezing all of the extruded scrap from between the lands 15accompanied by direct contact thereof or by the expansive actiondescribed above.

A skirt member 16 is adapted to receive one of the die halves in anaperture 16a extending through the skirt member 16. Although thespecific design of skirt member 16 is not important so long as theelements thereof combine to enclose upper die half 12 along its sideswhile leaving the die ends uncovered, the drawing shows the skirt member16 as having a body with opposed depending portions or skirts 17 alongthe longitudinal edges of aperture 16a. The aperture 16a is sized andshaped to hold the die half snugly therein, preventing relativehorizontal movement between the parts which could cause misalignment ofdie halves in the stamping operation. In the embodiment shown in thedrawings, the skirt member 16 is applied to upper die half 12, with thedepending skirts 17 thereof extending downwardly a short distance pastthe land 15. The inner surface of each of the skirts 17 generallyfollows the same contour as aperture 16a, engaging a substantial .andcontinuous part of the outer longitudinal edge of the land 15 to whichit is contiguous in a close sliding fit; however, the lowermost edge ofthe inner skirt surface is rounded or chamfered at 17a to provide alead-in surface, the purpose of which will be more fully explainedhereinafter. It should be noted that the body portion of skirt member 16covers only a part of each end of the outer vertical surface of upperdie half 12, and as a consequence, no part of the skirt member 16 isadjacent to or depends past the end portions of land 15 of upper diehalf 12.

As shown in FIGURE 5 the external stops mentioned above may be providedby a pair of laterally extending blocks 21 attached to the longitudinalsides of lower die half 13 by means such as machine screws 23. Each ofthe block 21 has a horizontal cross section substantially like that ofskirts 17 and is positioned so as to contact the lower surface 22 of theskirt 17 on the corresponding side of the die pair in use. The contactbetween surfaces 22 and the blocks 21 prevents the lands 15 from meetingin face-to-face contact to thus reduce wear and damage to theserelatively fragile surfaces. The preferred range of separation of lands1S caused by this stop means is from .005 down to approximately zeroinches.

One or more exhaust ports or vents 18, which extend through each of theskirts 17 at points aligned with the longitudinal sides of land 15,permit the escape of stamp die liquor and air which may be entrappedduring the stamping process. In the absence of such provision for (A) apair of mating die halves each having a cavity bounded by a continuousland, said lands being adapted to substantially contact one another inuse, each of said die halves having in the plane of its land a firstdimension and a second dimension which -is normal to said firstdimension,

(B) each said land comprising a pair of side portions extendingsubstantially in the direction of said first dimension, and a pair ofoppositely disposed end portions extending substantially in thedirection of said second dimension, said side portions of each landbeing oppositely disposed to one another and separated by the seconddimension of said cavity, each said end portion interveningcorresponding ends of said side portions whereby said side and endportions alternate on said land, and

(C) means to block extrusion of surplus plastic material from said dieoutwardly over the side portions of said lands and to permit extrusionover the end portions thereof in directions generally aligned with saidfirst dimension, said means comprising two spaced-apart andoppositelydisposed surfaces contiguous to and substantially coextensivewith the side portions of the lands of said die halves at least duringthe period of final deformation of said plastic material, one of saidsurfaces engaging one side portion and the second of said surfacesengaging the other side portion of the land of one die half, each ofsaid surfaces simultaneously engaging the mating side portion of theother of said die halves thereby preventing egress of surplus plasticmaterial in directions substantially aligned with said second dimension.

4. The die of claim 3 in which the Width of said-land .is approximatelyless than W5".

t 5. The combination of claim 3 in which said means is provided with amultiplicity of exhaust passageways aligned generally in the plane ofthe lands of said die halves when said halves are in full impressionposition, at least one exhaust passageway extending through each saidsurface.

6. The combination of claim 5 in which said exhaust passageways have adiameter of about 0.0156 to about 0.020.

7. A die for stamping a blank of plastic material into a pin-die shapedarticle, said die havingl in combination:

(A) a pair of mating die halves veach having a cavity bounded by aperipheral land, said lands being adapted to substantially contact oneanother in use, each of said die halves having co-planar of the landthereof a longitudinal dimension and a lateral dimension which is normalto said longitudinal dimension,

(B) said lands each having a pair of side portions substantiallyparallel to the said longitudinal dimension and a pair of end portionssubstantially parallel to generally aligned with said longitudinaldimension during stamping, said means comprising a pair of opposedskirts each of which has a length which is approximately the same asthat of a said side portion, each skirt being maintained in engagementwith substantially the entirety of the outer edge of a side portion ofthe land of one of the die halves, said opposed skirts extending beyondthe land of one die half in the direction of the other die half andbeing adapted to telescope over the outer edges of the side portions ofthe land of the other die half in close sliding contact therewith, saidskirts being separated from each other at their ends by the full lengthof each of said end portions of said one die half whereby oppositelydisposed unblocked areas intervene the mating end portions of said diehalves during the period of final deformation of said plastic material.

8. A die for stamping a blank of plastic material into a pin-die shapedarticle, said die having in combination: (A) a pair of mating die halveseach having a cavity bounded by a continuous land., said lands beingadapted to substantially contact one another in use, each of said diehalves having in the plane of its land a tirstdimension and a seconddimension which is normal to said first dimension,

(B) each said land comprising a pair of side portions extendingsubstantially in the direction of said first (C) a skirted member inwhich one die half is held in fixed relationship, said skirted membercomprising a body portion provided with an aperture for the reception ofsaid one die half and engaged with said one die half at points removedfrom the land, and a pair of opposed depending skirts integral with andextending from the body portion, said skirts being in close engagementwith and overlapping the outer edges of the side portions of the landsof the said one die half, said skirts being spaced apart at their endsby the full length of each of said end portions of the land of said onedie half, said opposed depending skirts being adapted to engage in closesliding contact with the outer edges of the side portions of the matingland of the other said die half.

References Cited in the tile of this patent UNITED STATES PATENTS thesaid lateral dimension, said side portions of -each 305,293 CollierSept. 16, 1884 land being oppositely disposed to one another and 724,771f AleXa -1 Apf- 7, 1903 separated by the lateral dimension of saidcavity, 769,173 Langguth Sept. 6, 1904 each of the said end portionsintervening correspond- 1,340,452 f Landstra May 18, 1920 ing ends ofsaid side `portions whereby said side and 50 1,680,823 Teed Aug. 14,1928 end portions alternate on said land, and 1,704,829 Grubman Mal- 12,1929 (C) means to block extrusion of surplus plastic mate- 2,195,399Engen Apr. 2, 1940 rial outwardly over the side portions of said lands2,621,368 Marshall Dec. 16, 1952 and to simultaneously directtheextrusion of sub- 2,818,604 f Miller et al Jan. 7, 1958 stantially allof said surplus material in directions the escape of liquor and air, theentrapped liquor or gas could prevent the soap from completely fillingthe die cavities in a lateral direction. It has been found that for bestoperation, the ports 18 should be sized to fall in the range of from.0156 to .020 in diameter.

As shown in FIGURES 2 through 5, several supporting pins 19 are driveninto holes drilled into the outer vertical surface of upper die half 12extending beyond the top of skirt member 16. The locations of the pinsare such that when the lowermost surfaces of the pins 19 contact the topsurface of the skirt member 16, the upper die half 12 is supported incorrect vertical alignment with skirt member 16 and the exhaust ports 18therein.

There are a multitude of ways in which the skirted die of this inventioncan be attached to a stamping machine. For example, an upper die platecould oe mounted over the assembled upper die half 12 and skirt member16 by being bolted to the skirt member 16 by means of the threaded holes20 shown in FIGURE 4, thus forcing and retaining pins 19 of the die half12 in contact with the skirt member 16, `and thereby eliminatingrelative vertical movement therebetween. Then the upper die plate couldbe fastened in some manner to an upper die platen which in turn isattached to the die plunger of the stamping machine. The lower die half13 could be similarly attached by means of a lower die plate and a lowerdie platen to the die slide of the machine. Since such means are wellknown in the art and play no part in this invention they have beenomitted from the drawing and from the detailed description of thisinvention in order to simplify the disclosure.

In the die set-up and in use, there is no need for the guide pins andguide bushings which are normally a part of the prior art dies forproducing pin-die shaped articles. The skirt functions to provide boththe preliminary alignment and the running guide needed during thestamping operation, in addition to the principal function hereinafterdescribed. The die set-up is facilitated by mounting the parts of thedie upon the stamping machine so` that one or both parts are free to beadjusted in location, bringing the die parts together into a fullimpression position, and then tightening or fastening such partssecurely to the machine While they are held in this position.

The function of the skirt in providing a running guide is important forgood stamping operation since there is usually at least a slight amountof play between the die plunger and the die slide parts of a stampingmachine. Such play is compensated for by the funneling effect of therounded or chamfered interior edges (lead-in surfaces) of the skirt 17,and by means thereof the lower die half 13 is deflected into registrywith the interior surface of the skirt 17 as the dies move together inuse, placing the die halves in perfect vertical alignment.

After the skirted die has been mounted upon the stamping machine, thestamping operation may be described as follows: A soap blank 11 of theproper size and plastic consistency and which has been treated withstamp die liquor is placed or fed between the die halves 12 and 13 whenthey are in the open position and the die halves are then broughttogether or into very close proximity under considerable force. As theopposed die halves approach each other, the intervening soap blank 11 issqueezed between the die cavities 14 of the die halves 12 and 13 andthus caused to be compressed in height and expanded in width. Uponcontinued relative movement as the die halves approach, the skirt 17telescopes over lower die half 13 and further deformation of the soapblank 11 occurs until finally the deformed blank fills the volumeintermediate the die halves iat a point in time prior to the time atwhich the die halves reach the full impression position. During thisinitial deformation period, any stamp die liquor and/or air which may beentrapped between the dies are exhausted through ports 18. Finaldeformation thereafter occurs until the die halves reach the fullimpression position, and it is during this phase that the principalfunction of skirts 17 comes into play blocking further expansion of thedeformed blank 11 in width and directing all surplus soap in asubstantially longitudinal direction so as to be extruded from the dieends. Lateral extrusion is effectively prevented by the close iit of theupper die half 12 in the aperture 16a of skirt member 16 and of thelower die half 13 with the inner surfaces of skirts 17 and by the skirtmaterial itself closing egress from between the die halves. Of course,an extremely small amount of soap will enter the ports 18 but such isinsignificant in its effect upon the bar quality when ports of thepreferred size (i.e., in the .0156 to .020 diameter range) are used.Along this same line it has been noted that during continuous operationof the skirted die of this invention, an extrusion of soap into ports ofthe preferred size does not prevent the escape of air and die liquortherethrough in subsequent stampings since the die is, in effect,selfcleaning in this respect.

As the opposed lands 15 are brought contiguous to one another at theconclusion of the final deformation of the blank 11, the pressureexerted upon any soap which lies between the lands causes substantiallyall of such soap t0 be extruded as scrap along with the other surplussoap -or to be forced into the bar being formed. In any event, at thefull impression position of the cycle or shortly thereafter, thesevering of the scrap from the formed bar is accomplished by thepinching off mechanisms previously described, and the extruded scrap ateach end falls into scrap receiving devices (not shown) adapted toreceive such material. Subsequently, the die halves may be moved to anopen position and the stamped bar removed by hand or by rotation of thedie halves or by other well known means so as to'prepare the dies forthe next stamping operation.

While previously dies for pin-die shaped articles frequently producedproducts having hairline cracks in the side and face panels (thelongitudinal sides and the top and bottom of the bar shown), the skirteddie of this invention produces articles having no such quality defect.It is believed that the extrusion of all the scrap in the direction ofthe grain of the soap blank, caused by the provision of blocking means(the skirts of the described embodiment) to prevent lateral scrapextrusion, is the factor which eliminates such hairline cracks.Furthermore, the skirted die of this invention permits a cleanseparation of scrap from product without auxiliary trimming devices andprovides for the concentration of such scrap at a few points so as tosimplify collection thereof.

Many modications `of the above invention may be used and it is notintended to hereby limit it to the particular embodiment shown ordescribed. For example, the die pair could be arranged to have the skirtmember inverted and mounted on the lower die half or the die 'halvescould possibly be operated in a horizontal plane. `The terms used indescribing the invention are used in their descriptive sense and not asterms of limitation, it being intended that all equivalents thereof beincluded within the scope of the appended claims.

What is claimed is:

1. In the process of die stamping crystalline oriented plastic materialinto a pin-die shaped article, the steps which comprise placing anoversize blank of said crystalline oriented plastic material betweenmating die halves, deforming said blank by means of said die halvesuntil scrap extrusion occurs and directing the extrusion ofsubstantially all of the scrap from between the die halves in thedirection of crystalline orientation of said blank.

2. The process of claim l in which said plastic material is milled andplodded soap.

3. A die for stamping a blank of plastic material into a pin-die shapedarticle, said die having in combination:

7. A DIE FOR STAMPING A BLANK OF PLASTIC MATERIAL INTO A PIN-DIE SHAPEDARTICLE, SAID DIE HAVING IN COMBINATION: (A) A PAIR OF MATING DIE HALVESEACH HAVING A CAVITY BOUNDED BY A PERIPHERAL LAND, SAID LANDS BEINGADAPTED TO SUBSTANTIALLY CONTACT ONE ANOTHER IN USE, EACH OF SAID DIEHALVES HAVING CO-PLANAR OF THE LAND THEREOF A LONGITUDINAL DIMENSION ANDA LATERAL DIMENSION WHICH IS NORMAL TO SAID LONGITUDINAL DIMENSION, (B)SAID LANDS EACH HAVING A PAIR OF SIDE PORTIONS SUBSTANTIALLY PARALLEL TOTHE SAID LONGITUDINAL DIMENSION AND A PAIR OF END PORTION SUBSTANTIALLYPARALLEL TO THE SAID LATERAL DIMENSION, SAID SIDE PORTIONS OF EACH LANDBEING OPPOSITELY DISPOSED TO ONE ANOTHER AND SEPARATED BY THE LATERALDIMENSION OF SAID CAVITY, EACH OF THE SAID END PORTIONS INTERVENINGCORRESPONDING ENDS OF SAID SIDE PORTIONS WHEREBY SAID SIDE AND ENDPORTIONS ALTERNATE ON SAID LAND, AND (C) MEANS TO BLOCK EXTRUSION OFSURPLUS PLASTIC MATERIAL OUTWARDLY OVER THE SIDE PORTIONS OF SAID LANDSAND TO SIMULTANEOUSLY DIRECT THE EXTRUSION OF SUBSTANTIALLY ALL OF SAIDSURPLUS MATERIAL IN DIRECTIONS GENERALLY ALIGNED WITH SAID LONGITUDINALDIMENSION DURING STAMPING, SAID MEANS COMPRISING A PAIR OF OPPOSEDSKIRTS EACH OF WHICH HAS A LENGTH WHICH IS APPROXIMATELY THE SAME ASTHAT OF A SAID SIDE PORTION, EACH SKIRT BEING MAINTAINED IN ENGAGEMENTWITH SUBSTANTIALLY THE ENTIRETY OF THE OUTER EDGE OF A SIDE PORTION OFTHE LAND OF ONE OF THE DIE HALVES, SAID OPPOSED SKIRTS EXTENDING BEYONDTHE LAND OF ONE DIE HALF IN THE DIRECTION OF THE OTHER DIE HALF ANDBEING ADAPTED TO TELESCOPE OVER THE OUTER EDGES OF THE SIDE PORTIONS OFTHE LAND OF THE OTHER DIE HALF IN CLOSE SLIDING CONTACT THEREWITH, SAIDSKIRTS BEING SEPARATED FROM EACH OTHER AT THEIR ENDS BY THE FULL LENGTHOF EACH OF SAID END PORTIONS OF SAID ONE DIE HALF WHEREBY OPPOSITELYDISPOSED UNBLOCKED AREAS INTERVENE THE MATING END PORTIONS OF SAID DIEHALVES DURING THE PERIOD OF FINAL DEFORMATION OF SAID PLASTIC MATERIAL.